Traditionally, the production of fungi such as mushrooms proceeds in a series of steps as follows:
providing a preparation of a solid nutritive medium (compost); PA1 optionally pasteurisation of the nutritive medium; PA1 inoculating the optionally pasteurized nutritive medium with fungal mycelia (spawn); PA1 arranging the inoculated nutritive medium in a growing environment; PA1 applying a substantially continuous layer of a casing material on the inoculated nutritive medium; PA1 allowing a colonization of the substantially continuous layer of the casing material with the mycelium of fungi; PA1 allowing the mycelium to form primordia of fruiting bodies and subsequently fruiting bodies from the substantially continuous layer of casing material; PA1 harvesting fruiting bodies of the fungi from the substantially continuous layer of casing material. PA1 Carbon about 64% PA1 Hydrogen about 5% PA1 Nitrogen about 1% PA1 Sulphur about 3% PA1 Oxygen about 27% PA1 i) loading of a mixer with a substantially dry raw material of mineral fibres; PA1 ii) optionally pre-mixing of the raw material of mineral fibres; PA1 iii) mixing of the raw material of mineral fibres with a simultaneous and controlled supply of a liquid to obtain a substantially flowable and non-dusting casing material, the supply of the liquid being controlled in such a manner that the raw material of mineral fibres, when sampled, is moisturized to an extent that a substantially homogeneous and flowable material of granules and/or agglomerates of granules of a mineral fibre structure is obtained.
The casing material will establish the conditions necessary for the growth of mycelia, and will support the formation of fruiting bodies of fungi, without a casing material. The formation of fruiting bodies has up to now been considered impossible.
Casing materials used in a traditional production lay-out of fungi, such as mushrooms, are normally based on peat.
Peat is not considered being a sterile material, and may, like any natural organic material consisting mainly of partly decomposed organic material such as sphagnum moss, contain pathogens harmful to the crop of fungi such as Trichoderma sp.
Peat has a natural low pH which must, in order to reduce the risk of attack of pathogens harmful to fungi, be increased to a pH of 7 or above by mixing a liming material into the peat casing. Being a natural organic material and due to the need of mechanical handling, the structure of peat will tend to break down and collapse in use, and as a result hereof the pore space within the peat casing material available for mycelial growth and/or water will be reduced. Moreover, as a result of a structural disintegration, water logged conditions will be established in the peat casing. This will lead to a poor gas exchange to and from the peat casing which in turn will lead to a reduced formation of fruiting bodies and thereby to financial losses for the grower.
Normally, very large quantities of peat, over 100,000 m.sup.3 per year in e.g. the United Kingdom alone, is used for the preparation of casing material in the production of fungi, and because peat is one of nature's resources it is likely that sources of peat (peat bogs) will be depleted or that availability will be restricted due to the legislation protecting the sites where peat is excavated.
Some attempts have been made to optimize the production of fungi using materials as casing layer that could reduce one or more of the above mentioned identified problems associated with the use of peat as a casing material as well as reduce the amount of a casing material used in the production of fungi.
Furthermore, there is an increasing need for the development of improved methods for growing fungi involving the application of alternative casing materials on a solid nutritive medium. Such casing materials having improved characteristics over known casing materials thereby being able e.g. to obtain a better yield and/or quality of produce.
Surprisingly, the present inventor has found that it is possible to establish mycelial colonization, pinning of fruiting bodies of mushrooms and subsequent formation of fruiting bodies in a casing material comprising granules or agglomerates of a mineral fibre structure arranged on a solid nutritive medium.
The following provides a review of the literature relating to the production of fungi and disclosing compositions containing mineral fibres used in the production of fungi.
Kokai (Japanese Patent Publication) No. 3-123417 discloses the use of a culture medium of "stone wool" (mineral fibres) having capillary action, immersed in a culture solution. Cultivation is conducted on the culture medium to fruit body of mushroom. It is stated that the liquid medium contains glucose, polypeptone, yeast extract, mono potassium phosphate, magnesium sulphate, calcium chloride, and trace amounts of other elements and water.
When the level of nutrients is lowered by the consumption of the mycelia, it is replaced by adding fresh culture solution to the culture medium.
However, this method is performed in an artificial environment, all organic nutritional matter being supplied via a liquid.
WO 89/05574 defines a casing material as a material which supports mushroom fruiting and a non-casing material as a material which will not support mushroom fruiting. According to the disclosure in WO 89/05574 "stone wool", in the form of a pad, had been inoculated with mushroom spawn and supplied with a nutrient source, but no colonization of the pad had been obtained. The "stone wool" tested is therefore a non-casing material which is used as a layer isolating the compost layer from the surrounding environment.
U.S. Pat. No. 4,170,842 describes a synthetic casing for mushroom beds provided by a formulation consisting of a water absorptive material selected from paper plant waste, spent mushroom compost and cotton seed hulls. The water absorptive material has been mixed with activated carbon, water and lime stone. The paper plant waste is said to be an example of a fibrous material which has little or no value and which may replace the costly peat as a casing material.
EP 0 284 421 discloses a synthetic substrate for the support of the growth and development of filamentous fungi. The substrate is comprised of a nutrient in a hydrated hydrogel matrix forming a capsule. In a preferred embodiment, the capsule is said to have an irregular external surface to allow filamentous fungi to adhere thereto.
H. R. Visscher in Proceedings of the 5th international congress on soilless culture, Wageningen 18-24 May 1980, pages 395-410, discloses a casing material based on lime-cakes, which is a clayey byproduct of sugar extraction from sugar beets, obtained as a CaCO.sub.3 precipitate, after clearing the hot sugar sap, and strained off as a slurry and afterwards pressed or weathered in the open in large basins. It is stated that studies had revealed that the lime-cakes must be a year old, turned and weathered; otherwise yield reduction will occur. To the lime-cake based casing material granulated "stone wool" has been added in amounts of 25 and 50% by volume, and tested as a casing material. However, it is stated that the yield obtained in such casing materials could not supersede yield obtained from peat.